Surgical Induction of Endolymphatic Hydrops by Obliteration of the Endolymphatic Duct

Abstract

Surgical induction of endolymphatic hydrops (ELH) in the guinea pig by obliteration and obstruction of the endolymphatic duct is a well-accepted animal model of the condition and an important correlate for human Meniere's disease. In 1965, Robert Kimura and Harold Schuknecht first described an intradural approach for obstruction of the endolymphatic duct (Kimura 1965). Although effective, this technique, which requires penetration of the brain's protective covering, incurred an undesirable level of morbidity and mortality in the animal subjects. Consequently, Andrews and Bohmer developed an extradural approach, which predictably produces fewer of the complications associated with central nervous system (CNS) penetration.(Andrews and Bohmer 1989)The extradural approach described here first requires a midline incision in the region of the occiput to expose the underlying muscular layer. We operate only on the right side. After appropriate retraction of the overlying tissue, a horizontal incision is made into the musculature of the right occiput to expose the right temporo-occipital suture line. The bone immediately inferio-lateral the suture line (Fig 1) is then drilled with an otologic drill until the sigmoid sinus becomes visible. Medial retraction of the sigmoid sinus reveals the operculum of the endolymphatic duct, which houses the endolymphatic sac. Drilling medial to the operculum into the area of the endolymphatic sac reveals the endolymphatic duct, which is then packed with bone wax to produce obstruction and ultimately ELH.In the following weeks, the animal will demonstrate the progressive, fluctuating hearing loss and histologic evidence of ELH. Petroleum lubricant is applied to the eyes to protect the animal from corneal injury due to drying. 3. The animal is shaved from the top of the head to the shoulders and between the ears. 4. The shaved area is prepped in a sterile fashion first with 7.5% povidone-iodine followed by 70% ethyl alcohol. 5. The animal is placed onto an operating table with warming blanket and onto a platform that elevates the head and flexes the neck. The head of the animal is directed away from the surgeon. Adequate flexion of the neck is required in order to adequately expose the occipital ridge. 6. The animal is draped in a sterile fashion.1. Bupivacaine plus epinephrine (Marcaine) 0.25% is applied along the prospective incision site (midline dorsal skin incision along the occiput).This causes local vasoconstriction, limiting bleeding, and provides lasting post-operative analgesia after the animal wakes. 2. Midline dorsal skin incision is made on the scalp along the occiput. 3. To gain adequate exposure, the skin is retracted laterally by placing a small curved hemostat on each side of the incision. 4. A horizontal incision is made along the neck muscle to expose the bony occiput. At this stage the animal may twitch despite adequate anesthesia due to transection of the greater occipital nerve. Spinal cord transection is a danger with horizontal incision into the suboccipit...

An epidemiological study to investigate the relationship between Meniere's disease and migraine

“…There are several theories as to the pathogenesis of Meniere's disease. The most accepted theory is that of endolymphatic hydrops with the vertiginous episodes being caused by contamination of perilymph with potassium‐rich endolymph due to rupture of Reissner's membrane. In their literature review, Foster and Breeze stated that published evidence supported the hypothesis that hydrops causes Meniere's disease.…”

Computer-aided detection and quantification of endolymphatic hydrops within the mouse cochlea in vivo using optical coherence tomography

“…Standardizing measurements is important to compare the different approaches for inducing endolymphatic hydrops in animal models. This includes surgical obliteration of the endolymphatic duct, 35 genetic mouse models of endolymphatic hydrops, 25 injection with lipopolysaccharide and/or aldosterone, 22 blast exposure, 27 and noise exposure. 19 As more images are collected from different researchers, an automated, objective method will be important for analyzing and comparing these large datasets.…”

Gentamicin delivery to the inner ear: Does endolymphatic hydrops matter?

“…A 0.5mm burr (Nouvag, Goldach, Switzerland) was used to drill from the medial to the operculum and into the endolymphatic sac and duct. The endolymphatic duct was then packed with aseptic bone wax using a straight pick and an otologic elevator and the skull defect was reinforced with Gelfoam (Pfizer, New York), according to a technique described elsewhere, and the wound was closed [ 25 ]. Postoperative analgesia with tramadol (5-10mg/kg 2id) was administered in the first 48 hours.…”